Separation of divalent transition metal beta-diketonates and their adducts by supercritical fluid chromatography

A method for separation and detection of divalent transition metal beta-diketonates by adduct formation/supercritical fluid chromatography (SFC) with an open-tubular capillary column and a FID detector is described. The crystal structures of copper (Cu)-hexafluoro-acetylacetone (HFA) and Cu bis(2,2,6,6-tetramethyl-3,5-heptanedionato) (THD) complexes have been determined by X-ray crystallography. The SFC behavior of Cu beta-diketonates shows a strong correlation with the structure of the complexes. The hydrated cu beta-diketonate complexes usually exhibit strong intermolecular interactions or decomposition in SFC. Formation of adducts with a neutral donor, such as tributyl phosphine oxide (TBPO), can greatly improve the SFC behavior and detection sensitivity of Cu(II) and Mn(II) beta-diketonates. The stoichiometry and thermal stability of the adducts Cu(II) and Mn(II) beta-diketonates with TBPO in supercritical CO(2) have also been investigated. The implications of utilizing adduct formation for supercritical fluid extraction (SFE) of divalent transition metals and for on-line coupled SFE/SFC analysis of divalent transition metals are discussed.     

Hydrogen-bonded urea-anion host lattices. Part 2. Crystal structures of inclusion compounds of urea with tetraalkylammonium bicarbonates

New inclusion complexes (C₂H₅)₄N⁺HCO ₃ ^– ·(NH₂)₂CO·2H₂O (1) and (n-C₄H₉)₄N⁺HCO ₃ ^– ·3(NH₂)₂CO (2) have been prepared and characterized by X-ray crystallography. Crystal data, MoK radiation:1, space groupP2₁/n,Z=8,a=9.356(1),b=29.156(4),c=12.161(1) Å, =90.03(1)°,R _F =0.062 for 2214 observed data;2, space groupP,Z=2,a=8.404(2),b=12.352(2),c=14.377(4) Å,a=88.20(2), =89.56(2), =71.68(1)°,R _F =0.052 for 3092 observed data. In both compounds the tetraalkylammonium ions are sandwiched between puckered layers, which are constructed from [((NH₂)₂CO)₂(HCO ₃ ^– )₂], ribbons, each composed of centrosymmetric hydrogen-bonded urea dimers and bicarbonate dimers, by lateral linkage through water molecules in1, and by direct cross-linkage of an alternate, parallel arrangement of the urea/bicarbonate and complementary urea ribbons in2. Supplementary Data relating to this article have been deposited with the British Library as Supplementary Publication No. SUP 82201 (40 pages).     

Preparation and characterization of Cr(CO)(4)dpp (chromium tetracarbonyl 2,3-bis(2'-pyridyl)pyrazine) adsorbed on silver nanoparticles

A transition metal carbonyl species, Cr(CO)(4)dpp, has been successfully attached to bare silver nanoparticles prepared by laser ablation of a metal foil in ethanol. Transmission electron microscopy (TEM) images have shown that at least a portion of the silver nanoparticles have been capped by the chromium species, and ligand shells corresponding to Cr(CO)(4)dpp multilayer adsorption onto the silver nanoparticles of 30-50 nm diameter have been observed. The detection of the strongest Raman-active nu(CO) band of Cr(CO)(4)dpp at 2004 cm(-1) revealed that the species has been adsorbed without decomposition. The time-of-flight secondary ion mass spectrometry (TOF-SIMS) signals recorded of the chromium-capped silver nanoparticles were also consistent with the nondecomposition adsorption process. Density functional calculations have been used to reproduce the Raman spectrum using Ag(7)(+) as a model surface. A large binding energy of about 122 kJ/mol has also been computed between silver and nitrogen atoms thus lending support to Cr(CO)(4)dpp being chemisorbed onto the silver surface.     

A comparison of protoporphyrin IX and protoporphyrin IX dimethyl ester as a photosensitizer in poorly differentiated human nasopharyngeal carcinoma cells

Protoporphyrin IX dimethyl ester (PME), a dimethyl esterification of protoporphyrin IX (PpIX), exhibits higher intracellular uptake into NPC/CNE2 cells, a poorly differentiated human nasopharyngeal carcinoma, than does PpIX. Phototoxicity studies reveal PME to be a more potent photosensitizer than is PpIX, at the early and late incubation time points. Correlating phototoxicity with subcellular localization indicates that PME is a more potent photosensitizer when its primary target of photodamage is mitochondria. Also, additional targeting of lysosome enhances phototoxicity.     

Noise-induced amplitude and chirp jitter in dispersion-managed soliton communications

An analytic theory is presented that demonstrates that noise-induced amplitude and quadratic chirp jitter in a dispersion-managed soliton system can impose a fundamental transmission limit. Using a variational method, we show that the nonlinear amplitude and chirp dynamics are well approximated by a two-dimensional random-walk process.     

Effect of power modulation on radical concentration and uniformity in a single-wafer plasma reactor

The effect of power modulation oil radical concentration and uniformity in a single-wafer plasma reactor was investigated with a radical transport and reaction model. Plasma etching of silicon using tetrafluoromethane under relatively high pressure (l torr) high frequency (13.56 MHz) conditions was taken as an example system. Gas velocity, temperature, and radical concentration profiles were obtained numerically by a finite element method. When compared to a contin uous wave plasma, power modulation can alter the relative concentration of radicals and in turn the each rate and uniformity as well as selectivity and anisotropy Uniformity is improved by power modulation except at high flow rates which, however, result in poor utilization of the feedstock gas.     

Crystal structure of trans-C2SnO5 pentagonal bipyramidal dibutylbis(phenylacetato)tin(IV) hydrate

The Lewis acidity of tin in a diorganotin dicarboxylate is demonstrated in this first example of a 1/1 adduct of the ester with a neutral ligand. The structure of dibutyltin bisphenylacetate hydrate [(C₄H₉)₂Sn(O₂CCH₂C₆H₅)₂·H₂O] has been determined from 1211 F ₀6F _c MoK reflections and refined to anR _F of 0.061 [space groupP2/a witha=8.416(2),b=10.391(5),c=14.28(1) Å,=98.42(4)° andZ=2]. TheC atoms [Sn-C 2.101(8) Å; C-Sn-C 169.9(5)°] make up the apices and the O_carboxylate [Sn-O 2.234(5), 2.439(7) Å; O-Sn-O 55.7(2)°] and O_water [Sn-O 2.342(8) Å] atoms the equatorial points of thetrans-C₂SnO₅ pentagonal bipyramid around the Sn atom. The molecular symmetry isC ₂, and the Sn and O_water atoms lie along a crystallographic twofold axis. The aqua ligand forms donor H-bonds with neighboring carboxylato groups to link the molecules into a double zigzag chain running parallel toa.     

Vortex dynamics in oscillatory chemical systems

Vortex core dynamics is studied in the Brusselator both near to and far from the Hopf bifurcation line for random and pair initial conditions. Extensive simulations are carried out for a pair of counter-rotating vortices close to the Hopf bifurcation line. Provided the vortices are not so far apart that wave-front annihilation produces strong gradients between their centers, the simulation results compare favorably with theories based on the complex Ginzburg-Landau equation. Far from the Hopf line the vortex core dynamics changes character and phenomena such as periodic motion of the vortex centers arise.     

On the use of fuzzy inference techniques in assessment models: part II: industrial applications

In this paper, we study the applicability of the monotone output property and the output resolution property in fuzzy assessment models to two industrial Failure Mode and Effect Analysis (FMEA) problems. First, the effectiveness of the monotone output property in a single-input fuzzy assessment model is demonstrated with a proposed fuzzy occurrence model. Then, the usefulness of the two properties to a multi-input fuzzy assessment model, i.e., the Bowles fuzzy Risk Priority Number (RPN) model, is assessed. The experimental results indicate that both the fuzzy occurrence model and Bowles fuzzy RPN model are able to fulfill the monotone output property, with the derived conditions (in Part I) satisfied. In addition, the proposed rule refinement technique is able to improve the output resolution property of the Bowles fuzzy RPN model.     

A hyperspherical transformation forecasting model for compositional data

Although Aitchison’s [Aitchison, J., 1986. The Statistical Analysis of Compositional Data, Chapman and Hall, London] method of logratio transformation of compositional data is widely used in various domains, it is limited by the assumption of a strict non-negativity of the components and the requirement of special treatments in practice of the zero components. We propose a dimension-reduction approach through a hyperspherical transformation that is capable of resolving the difficulty in maintaining non-negativity and unit-sum in forecasting compositional data over time. Applying the proposed model to a numerical simulation with a 4D compositional data embedded with zero components and forecasting the three production sectors in the Chinese economy both demonstrate the usefulness and validity of the new approach.